Despite enormous investments of financial and human resources, cancer remains one of the major causes of death. Current cancer therapies cure only about 50% of the patients who develop a malignant tumor. In most human malignancies, metastasis is the major cause of death.
Metastasis is the formation of a secondary tumor colony at a distant site. In most human malignancies, distant metastases are often too small to be detected at the time the primary tumor is treated. Furthermore, widespread initiation of metastatic colonies usually occurs before clinical symptoms of metastatic disease are evident. The size and age variation in metastases, their dispersed anatomical location, and their heterogeneous composition are all factors that hinder surgical removal and limit the concentration of anticancer drugs that can be delivered to the metastatic colonies. Therefore, detection of malignancies prior to dissemination of the tumor cells from the primary site is needed to enhance the effectiveness of current cancer therapies.
Aberrant glycosylation has been observed to be a common feature for most cancer types. Most of the carbohydrate antigens used for the diagnosis of human cancers carry polylactosamine structures, i.e., they contain Gal.beta.1.fwdarw.3/4GlcNAc. Polylactosamines are usually classified into two categories according to their polylactosamine unit structure. The polylactosamine having the Gal.beta.1.fwdarw.3GlcNAc structure is called the type 1 chain, and that having the Gal.beta.1.fwdarw.4GlcNAc structure is referred to as the type 2 chain. The most common tumor-associated antigens found in major human cancers have the lacto-series type 2 chain structure, which usually has been sialylated and/or fucosylated. Type 1 chain antigens are abundant in normal cells and tissues, and also are cancer-associated. For example, 2.fwdarw.3 sialylated Le.sup.a antigen (the CA 19-9 antigen defined by the N19-9 antibody) is a cancer-associated type 1 chain antigen. However, cancer diagnostic methods based on the detection of these known antigens have been hampered by high false positive and/or high false negative incidences.
Due to the difficulties in the current approaches to the diagnosis of cancer, there is a need in the art for improved compositions and methods. The present invention fills this need, and further provides other related advantages.